Imaging assembly with transparent distal cap

ABSTRACT

An imaging assembly for use in a medical imaging device such as an endoscope or the like. In one embodiment, the imaging assembly includes a transparent distal cap that is shaped to receive an image sensor insert. The image sensor insert has a cooling channel that supplies a cooling liquid or gas to one or more illumination sources.

FIELD OF THE INVENTION

The present invention relates to medical devices, and in particular tomedical devices that produce images of internal body tissues.

BACKGROUND

As an alternative to performing more invasive types of procedures inorder to examine, diagnose, and treat internal body tissues, manyphysicians are using minimally invasive devices such as catheters andendoscopes to perform such tasks. Such medical devices are inserted intothe body and routed to a point of interest in order to allow thephysician to view and treat the internal body tissues. Generally suchdevices include some sort of image producing mechanism, such as a fiberoptic imaging guide that transmits an image along a bundle of fibers toa proximal camera or eyepiece. Alternatively, video endoscopes orcatheters include a small image sensor that produces images of thetissue electronically.

In a conventional endoscope, the distal tip of the device is oftenopaque and includes one or more windows or lenses that are used for thedelivery of illumination light and an objective lens assembly for eithertransmitting an image to the proximal end of the endoscope or forfocusing an image on an image sensor. While the opaque distal tips havegenerally been proven to work well, improvements can be made.

SUMMARY

The invention described here relates generally to an imaging assemblyfor a medical device and in particular, with respect to one embodiment,includes a transparent distal cap and an image sensor insert that isfitted into the distal cap. The image sensor insert includes a coolingchannel that is thermally coupled to one or more illumination sources inthe image sensor insert. In one embodiment, opaque shields may be addedwithin the imaging assembly to prevent stray illumination light fromleaking to the image sensor.

In one embodiment of the present invention, the imaging assembly ispartially fitted within a metal ring of an articulation joint to shieldcircuitry in the imaging assembly.

In accordance with another embodiment of the present invention, thedistal cap includes one or more molded lenses.

In accordance with another embodiment of the present invention, athermistor is used to sense the temperature of the illumination sources.In one embodiment, the thermistor shares a common lead with theillumination sources and electronics that read a voltage across thethermistor compensate for a voltage on the common lead produced bycurrent in the illumination sources.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This summary is not intended to identify key features ofthe claimed subject matter, nor is it intended to be used as an aid indetermining the scope of the claimed subject matter.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood by reference to the following detailed description, whentaken in conjunction with the accompanying drawings, wherein:

FIG. 1 is an exploded view of an imaging assembly in accordance with oneembodiment of the present invention;

FIG. 2 shows the imaging assembly of FIG. 1 in an assembledconfiguration;

FIG. 3 is a rear view of an image sensor insert that is a component ofthe imaging assembly in accordance with an embodiment of the presentinvention;

FIG. 4 is a front isometric view of an image sensor insert in accordancewith an embodiment of the present invention;

FIG. 5 shows an imaging assembly including a distal cap, image sensorinsert, and a circuit board in an assembled configuration in accordancewith an embodiment of the present invention;

FIGS. 6A-6C illustrate a flex circuit and thermal clad circuit boardused in an imaging assembly in accordance with an embodiment of thepresent invention;

FIG. 7 illustrates how stray light from an illumination source can leakinto an image sensor; and

FIG. 8 illustrates how opaque sleeves can reduce the stray light inaccordance with another embodiment of the present invention.

DETAILED DESCRIPTION

As indicated above, the present invention is an imaging assembly for usein an endoscope or other medical imaging device. Although the disclosedembodiment of the invention is for use in an endoscope such as acolonoscope, bronchoscope, duodenoscope, and the like, it will beappreciated that the present invention is not limited to endoscopes butcould be used in other medical imaging devices, such as catheters, foruse in vascular, urinary, reproductive, ear, nose, and throat,applications, or the like.

FIG. 1 is an exploded view of an imaging assembly for an endoscope inaccordance with an embodiment of the present invention. The imagingassembly includes a transparent distal cap 20 that is positioned at thedistal end of the endoscope. An image sensor insert 50 is receivedwithin the cap 20. The distal cap 20 and the image sensor insert 50 aresecured to a distal portion of the endoscope shaft. In one embodiment,the assembly is secured to the distal most ring 100 of an articulationjoint of the type that includes a series of linked metal or conductiverings (not shown) that allow the endoscope to bend in a desireddirection under tension of one or more control wires.

In one embodiment, the transparent distal cap 20 is made of a plasticmaterial such as clear polycarbonate. The cap 20 has a distal face 22having a number of features molded therein. The distal face 22 includesa pair of windows 24 a and 24 b that allow illumination from anillumination source, such as LEDs positioned behind the windows, toreach the tissue to be imaged by the endoscope. In the embodiment shown,the windows 24 a, 24 b are flat, circular areas of clear plastic.However, lenses could be molded into the distal cap to change thepattern of illumination light distribution if desired.

In the embodiment shown, the windows 24 a and 24 b extend all the way tothe outer rim of the distal cap 20. This allows the rim to be madesmaller and to be smoothly rounded in order to provide increased patientcomfort and reduce the chance of injury to the patient.

Positioned generally between the windows 24 a and 24 b is an opening 26that is provided to receive an objective lens assembly for the imagesensor. Below the opening 26 for the lens assembly is an opening 28 thatserves as an entrance to a working channel of the endoscope. In oneembodiment, the rim of the cap 20 is beveled in the area of the opening28 to the working channel to provide a rounded edge and improve patientcomfort. A port 30 is adjacent the opening 28 to the working channel andis connected to a tube (not shown) in the endoscope for application of ajet wash liquid from the endoscope. A second port 32 is positioned atthe end of a nozzle that extends smoothly out from the edge of thedistal face 22 and bends over to distal face to direct water across thefront face of the objective lens assembly that is within the opening 26and/or the windows 24 a, 24 b that are in front of the illuminationsources. In addition, air or a gas can be delivered from the port 32 forinsufflation of the patient as needed.

The proximal end of the distal cap 20 includes a stepped region 36having a diameter slightly smaller than the diameter of the distalregion of the cap 20. Therefore, the proximal region 36 of the distalcap 20 can fit within an opening 102 of the distalnost ring 100 of thearticulation joint. The side surface of the proximal region 36 alsoincludes one or more notches 38 that receive corresponding tabs 104 onthe ring 100 of the articulation joint. The ring 100 may cover themajority of the sensor circuitry disposed at the distal tip of theendoscope, thereby providing electrical shielding to the circuitry whenthis ring is connected to an electrical ground.

The proximal end of the cap 20 also includes a flat receiving surface 40that is oriented in a direction generally perpendicular to the plane ofthe distal face 22. The receiving surface 40 divides the distal cap intoan upper portion and a lower portion. As will be described in furtherdetail below, the image sensor insert 50 is slideable on the receivingsurface 40 such that the components it holds are positioned behind thedistal face 22 of the cap 20.

The image sensor insert 50 comprises a generally semicircular componentwith a rounded upper portion 52 and a generally flat bottom surface 54.The bottom surface 54 rests on the receiving surface 40 of the distalcap 20 while the rounded upper portion 52 fits behind the upper portionof the distal face 22 of the cap 20. In the center of the image sensorinsert 50 is a cylindrical bore 56 into which an image sensor objectivelens assembly (not shown) is fitted. The cylindrical bore 56 alsoincludes a shoulder or lip therein to limit how far the objective lensassembly can be inserted into the bore 56 in order to aid in focusingthe lens assembly. In addition, the shoulder or lip helps to preventstray illumination light from reaching the image sensor.

In one embodiment, the image sensor objective lens assembly is formed ina lens barrel that secures the lenses and other components together as agroup. The barrel is adhesively or otherwise secured in the cylindricalbore 56 at a position that focuses the light onto the image sensor. Inanother embodiment, the lenses and other components of the objectivelens assembly can be held directly in the cylindrical bore 56 without alens barrel.

Surrounding the bore 56 is a semicircular cooling channel 58 in which acooling liquid or gas is passed. The cooling liquid or gas enters andexits at a pair of ports 60, 62 at opposite ends of the channel. Theports 60, 62 are coupled to tubes within the endoscope that deliver andreturn the cooling liquid or gas. A lip 64 surrounds the inner perimeterof the cooling channel 58 and provides a support for a circuit boardthat is seated within the channel 58, as will be described in furtherdetail below. A channel or notch 68 extends proximally from the front ofthe image sensor insert 50 over the curved upper portion 52 of the imagesensor insert 50 to allow passage of a current-carrying circuit or wiresthat carry current to the illumination devices and a thermistor on acircuit board, as will be described in further detail below.

FIG. 2 illustrates the distal cap 20 fitted within the distal ring 100of an articulation joint. The tabs 104 on the ring fit within thecorresponding notches 38 on the distal cap 20, thereby securing the twoparts together.

In final assembly, an outer sheath (not shown) covers the articulationjoint 100 and a seam 106 where the articulation joint meets the distalcap 20. In one embodiment, the sheath is made of a biocompatible polymersuch as polyurethane or the like.

FIG. 3 illustrates further detail of the image sensor insert 50 whenviewed from the rear or proximal end. Positioned on either side of theimage sensor insert is a pair of proximally extending legs 70 and 74.Each leg 70, 74 has a corresponding lumen 72, 76 therein that delivers acooling liquid or gas to the two ports 60, 62 that open to the coolingchannel 58. The lumen 76 is in fluid communication with the port 60 andthe lumen 72 is in fluid communication with the port 62 as shown inFIG. 1. Each of the legs 70, 74 also includes an inwardly facing step 78a, 78 b that provides a support for a circuit board to be secured to theimage sensor insert 50 as can be seen in FIG. 5.

The image sensor insert 50 also includes a recessed, rectangular imagesensor receiving surface 80 that is oriented in the same plane as thedistal face 22 of the distal cap 20. The image sensor receiving surface80 has a smaller circular or rectangular aperture 82 therein which opensto the cylindrical bore 56. The area surrounding the aperture 82 isgenerally flat so that an image sensor such as a CMOS or CCD imager (notshown) can be secured thereto with an adhesive or the like. In oneembodiment, the aperture is larger than the area that forms the image onthe image sensor so that no imaging pixels are wasted.

In the embodiment shown, one or more alignment bosses 86 are positionedat the sides of the image sensor receiving surface 80. The bosses 86 areconfigured as small semicircular protrusions on two sides of the imagesensor receiving surface 80 and serve to align an image sensorpositioned therein.

FIG. 4 shows further detail of the image sensor insert 50 from the frontor distal end. As indicated above, the image sensor insert has a shapethat is designed to be slideably received behind the distal face of thedistal cap 20. A raised lip 90 over the curved upper portion 52 of theinsert 50 limits the depth to which the insert can be fitted into thedistal cap 20. In the embodiment shown in FIG. 4, a semicircular thermalclad circuit board 150 is shown seated on the rim 64 surrounding thecooling channel 58. The circuit board 150 supports one or moreillumination LEDs 154 and 156 as well as a thermistor 158. Thethermistor is generally positioned above the cylindrical bore 56 thatreceives the imager objective lens assembly.

In one embodiment, leads that provide power to the LEDs 154, 156 as wellas leads that connect to the thermistor 158 are provided on a rigidcircuit board or by direct connect wires. In another embodiment, leadsthat provide power to the LEDs 154, 156 as well as leads that connect tothe thermistor 158 are included on a flex circuit. The flex circuit issecured to the circuit board 150 and extends over the top of the imagesensor insert through the channel 68 as shown in FIGS. 1 and 3.

As will be appreciated by viewing the bottom of the image sensor insert50 shown in FIG. 4, the bottom of the image sensor insert 50 isgenerally flat and does not contain any openings in order to protect theimage sensor and associated electronics from dirt, moisture, etc.,during assembly and use. In one embodiment, the image sensor insert 50is molded from a plastic material such as ABS acetyl butyl styrene.

FIG. 5 shows the image sensor insert 50 fitted within the distal cap 20.In addition, a circuit board 160 is seated in the steps 78 a, 78 b ofthe image sensor insert as shown in FIG. 3. In one embodiment, thecircuit board 160 is bonded to the steps 78 a, 78 b of the proximallyextending legs 70, 74 with an adhesive or the like. Also shown in FIG. 5are the lumens in the lower portion of the distal cap 20 that deliverthe gas/water to the ports on the distal face. A lumen 42 delivers waterto the lens wash port 32 and a lumen 44 delivers the insufflation gas tothe port 32. A lumen 46 delivers water to the jet wash port 30.

FIG. 6A shows a top side of a flex circuit 170 that provides power tothe LEDs and connects to the thermistor. On the top of the flex circuit170 is a series interconnect 172 that connects each of the illuminationLEDs in series.

The bottom side of the flex circuit 170 is shown in FIG. 6B. The bottomof the flex circuit includes a trace 174 that delivers current to theLEDs. A via 176 passes the current to the top side of the flex circuitand to the series interconnect 172. A second via 178 returns the currentfrom the top side of the flex circuit to the bottom side of the flexcircuit. A trace 180 returns the current delivered to the LEDs to itssource electronics. The bottom side of the flex circuit also includes apair of traces 182 that connect the thermistor to a circuit thatmeasures the temperature of the distal tip. If the temperature is toohigh, the current to the illumination LEDs can be reduced or theprocedure may be halted. It will be recognized that the pattern oftraces on the flex circuit is exemplary of an embodiment of the presentinvention.

FIG. 6C illustrates the thermal clad circuit board 150 on which theillumination LEDs and thermistor are mounted. As described above, thethermal clad circuit includes two pairs of pads 190, 192 upon which theillumination LEDs are bonded. The circuit board also includesinterconnects 194 for connecting the power to the LEDs. In addition, thecircuit board includes a pair of pads 196 positioned between the LEDsupon which the thermistor is bonded. The rear surface of the circuitboard 150 is clad with a heat conductive material such as copper, gold,silver, aluminum or other biocompatible material to transfer heat fromthe LEDs to the cooling liquid or gas flowing in the cooling channel 58.In some embodiments, the front surface of the circuit board 150 may becoated with a reflective material such as aluminum to direct lightemitted from the LEDs distally.

As shown in FIG. 5, the other end of the flex circuit 170 is preferablyinserted into a zero insertion force flex connector 200 on the circuitboard 160. The zero insertion force connector 200 provides a simple wayto assemble the distal tip without the use of complicated solderingoperations or jumpers. In one embodiment, the thermistor and the LEDsshare a common return lead extending from the circuit board 160 in thedistal tip to external electronics in a remotely located control cabinetin order to reduce the number of wires in the endoscope. However,current from the LEDs can induce a voltage on this common lead that isread at the control electronics as appearing across the thermistor. Thisincreased voltage can therefore make it appear as if the thermistor iscooler than it actually is. To compensate for this, the electronics cancompare the voltage across the thermistor with a reference voltage thatis based on the maximum drive current of the LEDs and the resistance ofthe common lead. Alternatively, the thermistor can have its own powerand return leads to obtain more accurate readings from the thermistor.

As it will be appreciated from the above, the present invention providesa simple assembly for housing the imaging components of an imagingendoscope or other medical imaging device. Because the distal cap ismade of a transparent plastic material, more light provided by theillumination components is able to reach the target tissue. Furthermore,because the distal tip is transparent, adhesive connections within theassembly can be cured by the application of curing energies, such asultraviolet light, into the distal tip.

Although the present invention is described with respect to itscurrently preferred embodiments, it will be appreciated by those skilledin the art that changes could be made. For example, it is possible toplace other components on the circuit board 150. For example, it may bedesirable to place one or more additional LEDs on the board or elsewherein the distal cap 20 to facilitate transillumination. Transilluminationinvolves lighting the distal tip of an endoscope or catheter so that itcan be seen from outside the body. A light source used fortransillumination should have good tissue penetration such as red LEDs.The light source may be pulsed or strobed to aid in its detection. Powerto the transillumination LEDs can be provided through the flex circuit.During transillumination, it may be desirable to darken the ambientlight surrounding the patient and to disable any flickering lightsources such as video display screens or the like in order to detect thelight emitting from the distal tip.

In some situations, light from the illumination sources may leak to theimage sensor when a transparent distal cap is used. For example, FIG. 7illustrates a transparent distal cap 250 on an endoscope or othermedical device. The distal tip includes LED illumination sources 252 and254. Light from those sources can reflect off the surfaces of the distalcap and otherwise leak to an image sensor 260.

In accordance with another aspect of the present invention, opaqueshields 270, 272, 274 are added in front of the illumination sourcesand/or the image sensor to reduce the light leakage and prevent lightfrom escaping in a direction other than through the windows in thedistal cap. The opaque shield 274 in front of the image sensor 260reduces light leaking indirectly to the image sensor. The opaque shieldsmay be molded cylinders or other shapes and made from a black or otheropaque plastic material. Alternatively, the shields may be made from anopaque film or coating placed in the cavities of the distal end cap.With the shields in place, only illumination light that is reflected offa tissue sample reaches the image sensor.

Although the present invention has been described with respect todisclosed embodiments, it will be appreciated that changes may be madewithout departing from the scope of the invention. For example, theillumination sources may comprise incandescent lights or fiber opticlight guides to deliver light produced from an external source.Therefore, it is intended that the scope of the invention be determinedfrom the following claims and equivalents thereof.

1. An assembly for an imaging medical device, comprising: a transparentdistal cap, said transparent distal cap having a distal face surfacewith a perimeter surrounding an entirety of the distal face surface; andan image sensor insert that is fitted within the transparent distal cap,the image sensor insert including: one or more illumination sources; acooling channel for removing heat from the one or more illuminationsources; a cylindrical bore adapted to accommodate one or more imaginglenses; and an image sensor; wherein the transparent distal cap includesone or more integral windows positioned in front of the one or moreillumination sources, wherein the one or more windows have an edge thatextends to the perimeter.
 2. The assembly of claim 1, wherein the imagesensor insert also includes a thermistor thermally coupled to the one ormore illumination sources.
 3. The assembly of claim 2, wherein thethermistor is positioned between the one or more illumination sources.4. The assembly of claim 1, wherein the one or more illumination sourcesare LEDs.
 5. The assembly of claim 4, wherein the image sensor insertincludes a flex circuit that delivers current to the LEDs.
 6. Theassembly of claim 5, wherein the image sensor insert includes a channelpositioned over the image sensor insert in which the flex circuit ispositioned.
 7. The assembly of claim 1, wherein the transparent distalcap is molded of a clear plastic material.
 8. The assembly of claim 1,wherein the edge of the transparent distal cap is rounded.
 9. Theassembly of claim 1, further including a transillumination light sourcepositioned behind the transparent distal cap that produces light tolocate a distal tip of the medical device.
 10. The assembly of claim 9,wherein the transillumination light source is an LED.
 11. The assemblyof claim 10, wherein the transillumination LED produces red light. 12.The assembly of claim 1, wherein the image sensor insert is generallysemicircular in shape.
 13. The assembly of claim 1, wherein thetransparent distal cap further includes an opening that serves as anentrance to a working channel and wherein a rim of the transparentdistal cap is beveled in the area of the opening.